Printing tele



Aug. 17, 1948. J. B. MOORE ETAL' 23,028

PRINTING TELEGRAPH SYSTEM Original Filed May '7, 1936 2 Sheets-Sheet 1 T U V INVENTORS I JOHN B. MOORE Er RICH DE.MATHES BY ATTO R N EY Aug. 17,1948. J. B. MOO RE EI'AL 23,028

PRINTING TELEGRAPH SYSTEM Original Filed May 7, 1956 2 Sheets-Sheet 2 INVENTORS JOHN B. MOORE 6 RIC R E. MATH ES ATTORNEY Reissued Aug. 17, 1948 UNITED STATES PATENT OFFICE PRINTING TELEGRAPH SYSTEM John B. Moore, Brooklyn, N. Y., and Richard E.

Mathes, Westficld, N. l, assignors to Radio Corporation of America, a corporation of Delaware Serial No. 790,600

1'7 Claims. 1

This invention relates to printing telegraph systems and more particularly to a system in which the circuits are subject to static interference and fading conditions.

Printing telegraph apparatus of the more generally used types employ five time elements for coding the signals representing each character to be printed. If these signals are sent over a radio channel or a carrier wave conductor channel they are very much subject to distortion and fading or to mutilation due to the presence of static impulses. The code signals, therefore, are liable to be received in an unintelligible form.

Accordingly, it is an object of our invention to provide a new method of code signaling for operation of printing telegraph equipment. It is a further object of our invention to provide the means for so actuating a printer in response to code signals that the correct characters will be printed so long as the signals are not mutilated, but that when a signal is mutilated by static or fading, then a misprint will be prevented.

It is a further object of our invention to provide means for causing the printer to produce an =1'ro1- indication if any character signal becomes unduly distorted or mutilated.

In carrying out our invention we propose to utilize a signaling code which in all cases comprises a uniform number of marking impulses. Thus, if fewer or more than the correct number of impulses for character selection is received, the master selector device at the receiver will lock out the printing mechanism and thereby prevent the printing of an incorrect character. In place of the character that would be incorrectly printed We can operate the master selector so as to cause an error indicating type bar to be actuated.

If instead of a five-unit code, we adopt a sevenunit code, taking either three or four of the seven elements at a time as marking pulses, it is possible to obtain thirty-five combinations. By the use of eight time elements, taking four at a time as marking pulses for each combination, there is available a total of seventy combinations, By taking only three at a time of the eight time elements a total of fifty six combinations is available.

Our invention will be described in more detail upon reference to the accompanying drawings, in which Figures 1 and 2 are code charts showing a specific arrangement of marking and spacing time elements suitable for selecting the type bars of a printin telegraph receiver to be actuated.

Fig. 3 shows in perspective certain details of a printer including the master selector bars and a few of the type bar selectors of which one is a selector for an error indicating type bar. Means are also shown for causing the printing mochanism to be locked out and the error indicating type bar to be selected when more or less than the proper number of marking impulses is received; and

Fig. 4 shows a circuit diagram of a modification of our invention wherein relays are used in place of step-by-step mechanical apparatus for obtain-- ing the selection of the error indicating typ bar when needed. I

The Baudot code which is in general use in printing telegraph systems is composed of five permutational time elements in any one of which a marking or spacing impulse may be transmitted. The character significance of each code signal is determined by the order of sequence of the marking and spacing impulses. In synchronous systems a continuous succession of five-unit code signals is transmitted. In the so-called startstop systems, however, a spacing impulse of fixed duration is utilized .to start the printer in operation for selecting each transmitted character to be printed. This spacing impulse is immediately followed by the five-unit code signal and then comes a stop-impulse of indefinite duration to arrest the printer operation until another type key on the keyboard is depressed. In the description to follow it will be understood that the marking and spacing impulses required for character selection are the only ones to be herein'considered since the use of additional impulses for operation band of a radio communications channel. It is,

however, only suitable for use on a circuit which is free from interference. Fading or noise of any kind results in errors in the received copy. Its use on radio circuits is, therefore, relatively limited. Another disadvantage of the five-unit code is that the number of combinations available is not sufficient to print all of the characters desired including letters, figures, punctuation marks, etc. Accordingly, it is the practice to employ a shift mechanism. It can easily happen that static impulses will produce such a code signal as to improperly actuate the shift mechanism 3 at the receiving end when the transmitting machine is still unshifted. The intelligence thus becomes garbled even without the knowledge of the transmitting operator.

The arrangement of marking and spacing impulses as shown in Fig. 1 may be considered from the standpoint that it is suitable either for a seven-unit code or for a portion of'an eight-unit For a seven-unit code the. marking and.

nal is composed of three marking impulses but.

these marking impulsesare differently arranged with espacing impulses interspersed. Itis equally possible; that four marking impulsesmight be used with the remaining portion oreach equal length-code signal filled in by spacingim-pulses. Itis also equally possible that a signallingcodemight" be adoptedin which each signal is composed of four marking and four, spacing impulses arranged indlfierent combinations.

Referring now to Fig. 3, we show one-embodiment of'the receiving apparatus which is suit able for use. with-code systems having a fixed number of marking units in each character sig=- nale' Only-thoseportionsota printing telegraph instrument are shown which relate tothe invention.

The master selector includes the conventional code selector bars 5 over which are the type character selectorbars 5. Duringthe reception ofacode signal any three of the bars 5 may be movedlongitudinally to-the left so as to bring into alignment certain notches 'linto-which aselected cross bar fi maydrop; Onlywhen the proper number of impulses is received during. the time-taken up by a-seven-unit-code signal will a. type bar selector 6' be permitted'todrop intov these-aligned notches. If more or fewerthan three impulses are received, the cross bars 6' will, allot them, be held up; by-the raised portions of the selector bars 5.

In orderto actuate an error indicating type bar, wehaveprovided.acountingdevice to be controlled by-thesuccessive actuations of the master selector-codebars 5. countingdevice includes an'escapement'wheel 8 mountedgaps. between the escapement-wheel teeth. After' each movement of onevof the code selector bars 5 the escapement pawls Illiand l5- -are returned totheirnormal. position under the tension of the spring ,I 6..

The various parts illustrated in Fig.- 3 havebeen shown in th.e position which. they wouldoccupy after.three,of ,thecodebars Shave been For an eight-unit actuated for selecting a character to be typed. The escapement wheel 8 has, therefore, rotated three steps from its initial position. It must be understood, however, that these three steps will be taken regardless of which particular code bars 5 are actuated, although in the illustration it is shown that the first three of these code bars viewed from the front of the device have been actuated. During the rotation of the escapement wheel B'a cam IT has been rotated through a like are so that a notch I8 in the face of this cam has come into alignment with a rider member I!) mounted on the end of the error indicating selector bar. 20. This bar 20 has accordingly been pulled slightly to the left under the traction of the spring 2|. In this position the selector bar 22 corresponding with the error indicating type bar has been restrained from dropping into the guide notches 23 of the code selector bars 5 by virtue of a raised portion 24 adjacent the notch N on the error selecting bar 20; In the code bars 5 the notches 23 are purposely made wider than some of the other notches in these bars in order that the selection of the crossbar 22 may be effected solely in response to the actuation of the error bar 20.

One of the type bar selectors 6a has been shown in the figure as having been lowered into the notches of the code bars 5 where these notches -;were brought into alignment by the actuation of the first three ofthese bars and by not actuating the remaining four bars. If one of these four remaining bars had been actuated the escapement wheel'would have taken a fourth step. None of the type bars for the printing of intelligence could be actuated in this case but in order to distinguish between the omission of a characterdue to a faulty signal and a normalspace between words, the error indicating type bar 'istpreferablyactuated'byLthe mocha This actuation can take place nism shown. either in .response to a deficiency or an excess in the: number of marking impulses in the code. Assume; for example, that the number of impulses was only two instead of three. In this case the notch l8 in thecam I! would not be in alignment :with the rider member l9 and, therefore, the notch N would be exactly under the barn permitting it to be lowered the same as forrthe: selection of any normal printing character; 1

In order to restore the escapement wheel 8 to'its norma'l position" uponcompletion of any printing operation, we preferably provide a rack and pinion mechanism connected in any suitable manner-with the driving mechanism for the printer. The rack bar 25 has been shown in the drawings as in its normal position, ready to make a. restoring movement. This movement is longitudinal 0f the bar and during its stroke to the left it engages with the pinion 22 rotating the same clockwise so asto wind up the spring M. The pinion 22 is loosely mounted upon the shaft 9 in order that its rot-ative movements may always be through the same arc regardless of the number of steps by which the escapement wheel Bhas been released. If an error has been detected by the reception of four or more impulses when three impulses were normal, then the pinion-22 and the shaft s will be rotated through a like arc in response to the full stroke of the restoring bar'25; If, however, the escapement wheel ,8 has taken fewer'than four steps; then while the pinion 22 is rotated through its full arc for a restoring operation, it will first bring the escapement wheel 8 back to its normal initial position, that is, with tooth designated 9 held by the escapement pawl Ill, and with the pin 21 resting against a stop 28. Further rotation of the pinion 22 will result in winding up the spiral spring 26 which is stiffer than the spring l4. Upon completion of the stroke of the restoring bar a pin 29 which has ridden over the top of the guide member 30 is now depressed into a channel below this guide member 39 under control of a spring 3|. This disengages the rack from the pinion 22 and if the spring 26 is under tension it will immediately unwind so as to reposition the pinion 22 in normal relation to the shaft 9; that is, with the two stop pins 32 and 33 pressing one against the other. The pin 32 is mounted on the shaft 9 while the pin 33 is mounted on the pinion 22. The normal engagement of these pins one with the other is maintained under tension of the spring 26.

Upon completing the return stroke of the restoring bar 25, the pin 29 mounted thereon is lifted out of the channel beneath the guide member 30 by virtue of a resilient sprin 34. This actuation of the restoring bar 25 will be understood to take place oincidently with the printing of a character. The mechanism for character printing and for actuation of the restoring bar 25 has not been shown because it is well within the skill of a mechanic to provide suitabl connections for carrying out the function of the restoring bar 25.

If the code signal should be mutilated by the occurrence of one or more static impulses so that at least four impulses are received during the transmission of a code signal, then further operations of the escapement member Ill-l5 will have no effect in releasing the escapement wheel 8 because after four steps the shaft 9 will be arrested from further rotation due to the engagement of its pin 21 with the abutment member 35. The number of teeth in the rack bar 25 is, therefore, limited to what are necessary for rotating the pinion 22, the shaft 9 and the escapement wheel 8 through the arc subtended by four teeth on the escapement wheel.

In certain instances it may be found preferable to employ a counting mechanism which comprises a system of relays as a substitute for the escapement wheel and escapement pawl mechanism shown in Fig. 3. Reference will, therefore, be now made to Fig. 4 in which such an electrical relay system has been shown diagrammatically.

In Figs. 3 and 4 corresponding parts, or parts possessing substantially the same functions, have been given like reference characters. In Fig. 4, for example, the code selector bars 5 have been similarly shown with teeth I3 and with notches I for selecting the type selecting cross bars 6. In this case, however, instead of actuating escapement pawls like those, I 9, l5, shown in Fig. 3, the teeth l3 are caused to lift a lever 36 against the pressure of a spring 31. This action takes place with each successive movement of the code bars 5. Contact is thereby made between the contact springs 38 so as to momentarily close a circuit from a source of potential 39 through different relays which are actuated in succession, Commencing with the first stroke of a code bar 5, an impulse is initiated from the source 39 through the contacts 38, through armature 42 and back contact 4| of relay 44, and thence through relay 4!] to ground. The closing of contacts 43 on the relay prepares a circuit which may be traced from the battery 39 through circuit breakin contacts 45, relay 44, contacts 43, relay 4D, and thence to ground. Current flows through this circuit immediately upon the opening of contacts 38, but not before, because during the operation of impulsing, which takes place when the lever 36 rides over a tooth l3, both terminals of the relay 44 are at the same potential. When relay '44 is energized the contacts 43 cause relay 49 to be locked up. Also the armature 42 of relay 44 is pulled away from the back contact 4| and into engagement with the front contact 46. This prepares relay 4'! for actuation in response to the second impulse. The second impulse may, therefore, be traced from battery 39, through contacts 38, armature 42, contact 46, armature 59, contact 49, relay 4'! and thence to ground. Upon the completion of this impulse and the opening of com tacts 38, relay 4'! locks up due to the closing of its contacts 5! and the establishment of a locking 'circuit from battery 39 through contacts 45 and relay 52. Upon the pulling up of the armature 59, a circuit is now prepared through the front c0ntact 53 and thence to the armature 54 of relay 55. The third impulse initiated at contacts '38 may then be further traced through back contact 59 of relay and relay 5'! to ground. When relay 55 is actuated in response to the opening of the contacts 38 and the closing of the locking contacts 60 a circuit is established from battery 39 through circuit breaking contacts 45 and the serially connected relays 55 and 51.

Relay 55 has two armatures 54 and 63 both of which are pulled up simultaneously upon the breaking of the impulsing circuit at the contacts 38. Armature 54 upon contacting with the front contacts 'll prepares a circuit fora possible fourth or any subsequent impulse through relay 61. Armature 63 upon contacting with its front contact 64 feeds current from the battery 39 through circuit breaking contacts 45, contacts 64 and 58 and thence through a magnet 52, to ground. The function of magnet 62 is to pull up its armature lever 65 to which is connected the error bar 20. In the embodiment of our invention shown in Fig. 4, the error bar 29 is normally held in position for selecting the type bar 22 having an error indicating character thereon. It is only when a character selection consists of three marking impulses, no more and no less, that the magnet 62 is actuated. The notch 25 is at that time withdrawn from beneath the bar 22 and prevents its selection. Any one of the type bars 6 may, however, be selected according to the code combination set up in the code bars 5.

Assuming now that a fourth code bar were to be actuated by a static impulse so as to mutilate the code signal, then the impulse produced at the fourth time of closing the contacts 38 will be directed through the armature 42, front contact 46, armature 59, front, contact 53, armature 54, front contact H and thence to the relay 6'! which is grounded. This relay immediately locks up through the closing of contacts 72 and simultane ously it breaks connection between the contacts 58 which are disposed in the energizing circuit for the magnet 62. Now although all of the relays 49, 44, 41, 52, 5'1, 55 and 5? are locked up, magnet 62 becomes de-energized and permits of the selection of the error indicating type bar 22, the same as when only one or two impulses of the sevenunit code signal had been received.

Simultaneously with the printing of a character the restoring bar 25 is mechanically actuated. The mechanism for doing this has not been shown because it is well within the scope of an ordinary 7 mechanic to provide it. The circuit. breaking contacts 4 5 are, therefore, opened for the. purpose of unlocking all of the relays which had been successively actuated during the counting operation. The relay system is thus prepared for counting the impulses of a succeeding code signal.

Weclaim:

1. In a printing telegraph system means responsive to character representing signals all of which signals are of equal length and possess a fixed-ratio other than one-to-one between the number of marking and spacing units thereof, means to de-code said signals, and actuating mechanism responsive to the operation of said tie-coding means to printa designated character only when a signal is received the marking and spacing units of which are in conformity with said fixed ratio.

:2, In a printing telegraph system a plurality of type bar selectors, means including a plurality of decoding elements cooperative with said selectors for making character selections only when azpredetermined invariable number of said ele ments has been caused to respond to the con trolling impulses of a code signal, an error-indicating device, and-means controlled solely by the count of said controlling impulses and operative in response to the reception of an excess or deficiency thereof within the time interval allotted to said code signal for actuating said error-indicating device.

-3. A printing telegraph apparatus having a plurality of de-coding members each 'actuable in response to the reception of a marking element of a code signal, and type selecting elements each selectable only upon the actuation of a fixed normal number of said de-coding members other than one-half the'total number thereof,

4. In a printing telegraph system, receiving apparatus having a plurality of decoding members each actuable in response to the reception of a marking element of a code signal, type selecting elements each selectable only upon the actuation of a fixed normal number of said decoding members, means including an additional type selecting element for indicating the reception of a mutilated signal and means rendered effective upon receipt of an abnormal number of marking impulses within a fixed time interval allotted to a code signal for then actuatin said additional type-selecting element to cause an error-designating character to be printed in place of such character as would correspond to the signal before mutilation thereof.

5..In a telegraph system, code signal receiving apparatus, a receivingprinter having character selecting elements, de-coding means operable in response to signals having a permutational arrangement of marking and spacing units, the number of said marking units being in fixed ratio to the spacing units, for determinin the sequence of operation of the character selecting elements, and means operable in sole dependence upon a departure from said fixed ratio for causing said printer to print an error-designating character.

6. A system in accordance with claim 5 and having an impulse counting device mechanically associated with said decoding means and fully controlled thereby for determining instances when mutilated signals are received.

'7. A system in accordance with claim 5 and having a. relay network operable under the full control of saidde-coding means for effecting an error-key selection upon-receipt of a mutilated signal.

-8. In a device of the class described, printing mechanism operable in response to the receipt of code signals having a uniform number. of marking elements and a uniform number of spacing elements, an error-designating key, and means for actuating said key solely in response to the receipt of a signal which lacks conformity with the usual number of marking and spacing elements.

9. A device in accordance with claim 8 and having an escapement mechanism operable stepby-step upon receipt of each marking element of a code signal and means operable by said escapement mechanism to select for actuation the error-designating key when the number of marking impulses received during a time interval allotted to a code signal is either excessive or deficient.

10. A device in accordance with claim 8 and having a relay system operable to count the number of marking elements of a code signal and to make selection of the error key when the number of marking impulses received during the fixed time interval allotted to a code signal is either excessive or deficient.

11. The method of indicating the reception of a mutilated character code signal over a telegraph system by ignal elements having selecting and non-selecting functions which comprises allotting an invariable time interval to each code signal, employing a code in which each signal possesses an invariable ratio between the elements having selecting and non-selecting functions, counting the selecting elements in each said time interval and causing an indication to be made when there is an excess or deficiency in said selecting elements.

12. In a telegraph receiving system, recording means responsive to code signals havin a uniform number of elements of a certain characteristic plus elements of a difierent characteristic, an error indicating device, and means responsive to the receipt of a code signal having an abnormal number of elements of said certain characteristic for actuating said error indicating device, said means comprising a first series of impulse-responsive devices and a second series of devices each responsive upon the cessation of an impulse through an associated one of said impulse-responsive devices, and circuits interconnecting the devices of the two series in such manner that they act as impulse counting relays for preventing the operation of said error indicating device upon reception of a correct code signal.

13. In a printing telegraph system, means responsive to character representing signals of equal length, means to decode such of said signals as possess a normally fixed ratio between the number of marking and spacing units thereof, actuating mechanism responsive to the operation of said decoding means to print a designated character, and error designating means responsive to the reception of a signal wherein the marking-to-spacing unit ratio is other than the one normally fixed.

14. A printing telegraph apparatus having a plurality of de-coding members each vactuable in response to the reception of a marking element of a code signal, type selecting elements each selectable by an appropriate combination of a normally fixed number of said de-coding members, and means effective whenever a received code signal contains an excess or deficiency of marking elements With respect to said normally fixed number for preventing the selection of said type selecting elements.

15. A printing telegraph apparatus having a plurality of de-coding members each actuable in response to the reception of a marking element of a code signal, type selecting elements each selectable by an appropriate combination of a normally fixed number of said de-coding members, an error indicating device, and means effective whenever a received code signal contains an excess or deficiency of marking elements with respect to said normally fixed number for actuating said error indicating device.

16. In a printing telegraph system, a plurality of type bar selectors, means including a plurality of decoding elements cooperative with said selectors for making character selections in response to the reception of any one of a number of different code signals all of which are characterized by an invariable number of controlling units, and means controlled solely by the count of said controlling units and operative in response to the reception of an excess or deficiency thereof within the time interval allotted to a single code signal for preventing the operation of the first said means.

17. A telegraph receiving system comprising means responsive to character representing signals of equal length, means to decode such of said signals as possess a normally fixed ratio between the number of marking and spacing units thereof, apparatus under control of said decoding means for recording the characters represented by said signals, and a utilization device operable in response to the reception of a signal wherein the marking-to-spacing unit ratio is other than the one normally fixed.

JOHN B. MOORE. RICHARD E. MATHES. 

